Children's success or failure in the early school years is an important predictor of a range of developmental outcomes. Despite our understanding that these predictive relations exist, we know very little about how trajectories of low versus high achievement are produced, particularly with respect to the developmental precursors of early academic skills. The proposal describes a novel longitudinal biobehavioral study of a diverse sample of 350 children from age 4 to first grade, using a multi-method approach to study trajectories of emotional and cognitive processes and the emergence of academic skills and social skills competence at the transition to school. We propose to examine learning engagement across preschool and early childhood as the mechanism mediating children's early emotional, cognitive, and social skills and later school success as measured by trajectories of academic achievement and social skills in first grade. Further, we propose to examine the contextual factors in home and school that moderate the relations between these early skills and learning engagement. Learning engagement is defined as positive affect associated with school and learning, interest and persistence in challenging academic tasks, and active participation in classroom activities. We propose that these indices of learning engagement emerge and become integrated as a function of earlier emotional and cognitive skills, making this program of research uniquely positioned to elucidate school-relevant processes that have to date been either unexplored or not well-linked to prior developmentally significant skills. By understanding the emergence of learning engagement and how it is affected by child and environmental factors as well as the interaction between them, we can develop more effective intervention approaches to increase academic achievement and support children's adjustment.